Effect of nitrogen flow rate on structure and properties of nanocrystalline TiN thin films produced by unbalanced magnetron sputtering

Nanocrystalline TiN thin films were deposited on (100) silicon wafers using an unbalanced magnetron (UBM) sputtering system. The structure and properties of the TiN thin films were studied under single-variable experimental condition by varying nitrogen flow rate ranging from 0.25 to 1.75 sccm. The grain size of the films was determined by X-ray diffraction (XRD), and the size was less than 7 nm. The images of transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM) also showed a nanometer-size grain structure of the TiN thin films. The N/Ti ratio increased (N/Ti=0.4-1.1) while the deposition rate decreased with increasing nitrogen flow rate. The preferred orientation changed from (111) to (200), then back to (111) as the nitrogen flow rate increased. There was no significant variation in the film hardness with nitrogen flow rate or preferred orientation. It is noted that the film hardness was high, ranging from 23.4 to 27.6 GPa, even for the film thickness down to 140 nm. The resistivity decreased with increasing packing factor. Ti/TiN nano-composite was found in the films with N/Ti ratio below 0.6.